In a manufacturing process of a semiconductor apparatus, various gas processes such as a film forming process, an etching process and the like are performed on a semiconductor wafer as a target substrate (hereinafter, referred to as a “wafer”). These gas processes are carried out by supplying a reactant gas (corrosion gas), e.g., a processing gas containing halogen, e.g., Cl, F or the like, from a shower head provided at an upper portion of a chamber accommodating therein a wafer while depressurizing the interior of the chamber. For example, in a CVD film forming process for forming a Ti-based film, e.g., Ti, TiN or the like, the film forming process is performed by introducing TiCl4 gas as a processing gas (film forming gas), a reduction gas and the like into a chamber in a predetermined depressurized atmosphere. At this time, a wafer is heated to, e.g., about 450 to 700° C., and the processing gas is converted into a plasma, if necessary.
When the film forming process is repetitively carried out, by-products are adhered to a shower head, a chamber wall and the like. These adhered by-products are peeled off and become particles. Therefore, dry cleaning is performed by supplying a cleaning gas into a chamber regularly or when necessary. Further, as for a cleaning gas, ClF3 gas is widely used because it can almost completely clean an interior of a chamber without a plasma (e.g., Japanese Patent Laid-open Application No. H10-189488).
However, ClF3 gas easily reacts with Al, Ni, Ni-based alloy as a material forming a chamber in a processing apparatus, and carbon, SiN, AlN or the like as a material for forming a heater or a stage of a substrate. For that reason, a cleaning temperature needs to be decreased to about 200° C. Accordingly, a period of time to increase or decrease the temperature in the chamber is required between the film formation and the cleaning, thus severely deteriorating the productivity of the semiconductor apparatus manufacturing process.
Meanwhile, Japanese Patent Laid-open Application No. H10-312976 describes a technique in which Cl2 gas is used as a cleaning gas and a cleaning temperature is about 625° C. The cleaning temperature thereof is higher than that of ClF3 gas, and the cleaning can be performed near the film forming temperature. Hence, it is considered that the productivity does not deteriorate.
However, the technique described in Japanese Patent Laid-open Application No. H10-312976 does not specify the detailed conditions of the cleaning process. Further, it is unrealistic to completely remove the by-products, or damages are inflicted on the chamber wall or in-chamber members. Besides, regardless of the existence of the above Patent Document, the cleaning process using a chlorine-based gas such as Cl2 gas or the like has not been practically employed.